Conventional golf balls can be divided into two general types or groups: solid balls and wound balls. The difference in play characteristics resulting from these different types of constructions can be quite significant.
Balls having a solid construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Solid balls are generally made with a single solid core, usually made of cross-linked rubber, which is encased by a cover material. Typically the solid core is made of polybutadiene which is chemically cross-linked with zinc diacrylate and/or similar cross-linking agents and is covered by a tough, cut-proof blended cover. The cover is generally a material such as SURLYN®, which is a trademark for an ionomer resin produced by DuPont. Such a combination imparts a high initial velocity to the ball that results in improved distance. Because these materials are very rigid, two-piece balls can, depending on the construction, have a hard “feel” when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate, which provides greater distance.
Wound balls typically have either a solid rubber or liquid center core around which many yards of a stretched elastic thread or yarn are wound. The wound core is then covered with a cover material such as balata or polyurethane. Wound balls are generally softer and provide more spin, which enables a skilled golfer to have control over the ball flight and direction. Particularly, with approach shots into the green, the high spin rate of soft, wound balls enables the golfer to stop the ball very near its landing position, if desired.
The design and technology of golf balls has advanced to the point that the United States Golf Association (“USGA”) has instituted a rule prohibiting the use of any golf ball in a USGA-sanctioned event, that can achieve an initial velocity of 250 ft/s, when struck by a driver having a velocity of 130 ft/s. (referred to hereinafter as “the USGA test”.)
Manufacturers place a great deal of emphasis on producing golf balls that consistently achieve the highest possible velocity in the USGA test without exceeding the limit. Because of this, golf balls are available with a range of different properties and characteristics, such as velocity, spin, and compression. Thus, a variety of different balls are available to meet the needs and desires of a wide range of golfers.
Regardless of the construction, players generally seek a golf ball that delivers maximum distance. Balls of this nature obviously require a high initial velocity upon impact. As a result, golf ball manufacturers are continually searching for new ways in which to provide golf balls that deliver the maximum performance for golfers at all skill levels, and seek to discover compositions that allow a lower compression ball to provide the performance generally associated with a high compression ball.
The physical characteristics of a golf ball are determined by the combined properties of the core, any intermediate layers, and the cover. The physical characteristics of each of these components are determined by their respective chemical compositions. The majority of components in golf balls consist of linear polymers. This linear nature affords diverse physical and mechanical properties. The physical properties of linear polymers are highly dependent on molecular weight. Two examples of such properties are solubility and viscosity. As the molecular weight increases, the viscosity of the material increases. This can be a beneficial property if a viscous material is desired, but in many industrial processes, e.g., where injection molding is the processing method of choice, extremely viscous materials slow down the process and viscosity can become a limiting step of production. Also, as molecular weight increases, the solubility decreases. In many applications such as the manufacture and use of coatings or covers or films from liquids, low solubility leads to difficult manufacturing problems. Thus, there is a need for materials that have much lower viscosity and much higher solubility than linear compounds, yet still retain the advantageous properties of linear compounds. These properties would make such materials ideal commercial candidates for use as additives or property modifiers for golf equipment components and, in particular, golf ball components.
The compositions of the present invention typically include polymer(s) comprising at least one dendritic macromolecule. Dendritic macromolecules provide a reduction in viscosity and increased compatibility with other polymeric components, in injection molded, compression molded, or cast material components in golf balls. The present invention further provides the tools and mechanisms to promote adhesion and compatibility in golf ball components that are formed with at least one dendritic macromolecule functionalized with at least one graftable or reactive site. The inherently low viscosity and increased solubility of hyper-branched polymers to generate low VOC, durable inks and coatings for golf balls and golf clubs.